Responses of Multipurpose Tree Species to Two Successive Summer Droughts after Transplanting

An experiment was conducted to determine relative drought tolerance of multipurpose tree species. Five important fuel, fodder and timber tree species namely, Grewia optiva, Morus alba, Dalbergia sissoo, Acacia catechu and Populus deltoides, during first and second summer drought period from April to June (75 days) exhibited differential responses at physiological levels. Xylem water potential (ψ), photosynthesis, transpiration, drought tolerance efficiency, drought injury index and mean daily productivity were significantly less in water stressed plants within each species compared to unstressed plants during first and second summer droughts. Out of the five-agroforestry tree species, physiological attributes were more adversely affected in G. optiva, A. catechu and P. deltoides in comparison to M. alba and D. sissoo. Morus and Dalbergia were able to maintain highest xylem water potential up to 75 days under water stress, whereas G. optiva and P. deltoides recorded the lowest values during the first and second summer drought. Photosynthesis and transpiration rate was reduced to a greater extent in G. optiva, A. catechu and P. deltoides as compared to M. alba and D. sissoo. Drought injury index was minimum in M. alba, followed by D. sissoo, whereas drought tolerance efficiency was maximum up to 75^th day. P. deltoides exhibited maximum injury index during both the summer droughts. Inhibition of mean daily productivity over control was more in G. optiva, A. catechu and P. deltoides in comparison to M. alba and D. sissoo. The results of this study have exhibited relatively better drought tolerance of M. alba and D. sissoo as compared to G. optiva, A. catechu and P. deltoides.